LITTLE ROCK, Ark. (AP) - The Arkansas Senate voted Tuesday to override Gov. Mike Beebe's veto of legislation that would ban most abortions from the 12th week of pregnancy onward and would give the state the most restrictive abortion laws in the country.

The Republican-led Senate voted 20-14 to override the veto. The state House hadn't yet voted on it. Only a simple majority is needed in each chamber to override a veto in Arkansas.

Abortion rights proponents have said they would sue to block the 12-week ban if it's approved. Its 12-week standard is based on when a fetus' heartbeat can typically be detected through an abdominal ultrasound.

The Legislature last week overrode Beebe's veto of a ban on most abortions from the 20th week onward. That law is based on the disputed claim that fetuses can feel pain by then.

On Monday, Beebe vetoed the 12-week ban for the same reason he vetoed the 20-week measure. He said both measures are unconstitutional and contradict U.S. Supreme Court's 1973 Roe v. Wade ruling, which legalized abortion until a fetus can viably survive outside the womb. A fetus is generally considered viable at 22 to 24 weeks.

The 12-week ban would prohibit abortions when a heartbeat is detected using an abdominal ultrasound. It includes exemptions for rape, incest, the life of the mother and highly lethal fetal disorders. The 20-week prohibition includes all of the same exemptions except for fetal disorders.

The measure is among several abortion restrictions lawmakers have backed since Republicans won control of the House and Senate in the November election. Republicans hold 21 of the 35 Senate seats, and 51 of the 100 seats in the House. It takes a simple majority in both chambers to override.

Beebe has signed into law one of those measures, a prohibition on most abortion coverage by insurers participating in the exchange created under the federal health care overhaul.

Unlike the 20-week ban, which took effect immediately, the 12-week restriction won't take effect until 90 days after the House and Senate adjourn. Lawmakers aren't expected to wrap up this year's session until later this month or April.

In vetoing both measures, Beebe has cited the costs to the state if it has to defend either ban in court. The American Civil Liberties Union of Arkansas has vowed to sue if the state enacts the 12-week ban and the group said it was considering legal action over the 20-week restriction as well.

Beebe noted that the state paid nearly $148,000 to attorneys for plaintiffs who successfully challenged a 1997 late-term abortion ban.

The original version of Rapert's bill would have banned abortions as early as six weeks into a pregnancy, but he changed the measure after facing resistance from some lawmakers worried that it would require a vaginal probe.

Women who have abortions would not face prosecution under Rapert's bill, but doctors who perform abortions in violation of the 12-week ban could have their medical licenses revoked.